1. Field of Invention
The present invention relates to a device for removing objects from passages and the human body, in more particularily to an extracting device for removing kidney stones from the urinary tract.
2. Description of the Prior Art
The formation of stones in the kidneys has been a very serious problem for many years. Such stones, which are formed from calcium or other particulate matter, generally are hard in the form of irregular masses. It is common for these stones to attempt to pass through the ureter, to the urinary bladder. In addition to being extremely painful to the patient, the stones may cause blockage of the urine producing ureteral colic. In some instances, stones will pass normally by the peristalic waves of muscle contracture into the bladder. On the other hand, this action may force an irregular sharp stone into the lining of the ureter, causing swelling or edema which in effect reduces the size of the ureteral lumen.
Stones having a diameter of more than 0.5 centimeter and irregular stones may not pass spontaneously and generally require surgical intervention or extraction.
The most narrow portion of the ureter is the first inch beyond the kidney pelvis and the last inch near the urinary bladder, called the uretero vesical junction. These two locations are the most likely points which will prevent spontaneous passage of a stone. It has been known in the prior art to extract a stone from the uretero vesical junction by means of a "stone basket". These wire basket devices are passed through a cystoscope and into the ureter where they are guided up beyond the stone, if possible. The physician attempts to capture the stone in the wire basket and extract it. However, it is not always possible to pass the device beyond the stone, and the stone may be pushed back into the renal pelvis and lost. Additionally, there is a significant danger of injuring the ureter or even perforation thereof. Also, the stone basket can scrape and injure the ureter from the wires of the basket and from the irregularly shaped stone.
Extractors have been proposed in the prior art which attempt to overcome the disadvantage of the wire basket extractor by the use of catheters having balloons attached to the distal end thereof. For example, one prior art device utilizes a single catheter with two inflatable balloons concentric with the catheter near the distal tip. The catheter is adjusted so that an arrested stone is between the balloons, the balloons inflated and the catheter slowly withdrawn such that the lower balloon dilates the ureter and the upper balloon pushes the stone toward the bladder. However, the stone must be relatively small since it is required to be caught between the catheter and the ureter wall.
An improvement to the two balloon catheter has been provided by Shiahata in U.S. Pat. No. 4,295,464. Here, a double catheter is provided having a balloon at the distal end of each and which provides relatively movement between the two balloons. Although an improvement, the size of the stone which can be captured is limited by the catheter size and the mechanical design of the catheter is relatively complex. A single balloon catheter having a double lumen is taught by Beecher in U.S. Pat. No. 424,243,040. Beecher teaches the use of concentric catheters with the inner catheter movable within the outer catheter. An inflatable balloon is attached at the distal end of the outer catheter and at the distal end of the inner catheter such that the balloon may be inflated by pressure in the lumen formed between the inner and outer catheter. The lumen of the inner catheter provides a clear passage to which a vacuum pump may be connected to produce suction which will permit pulling the stone into the balloon when inflated. The requirement for producing relative motion between the inner and outer catheters requires careful handling on the part of the physician and also results in the device being is relatively complex and expensive to manufacture.
Thus, there is a need for a catheter capable of extracting stones from the ureter which can be manufactured at low cost and therefore be disposable after use, and which will capture a stone in such a manner that no damage can occur to the ureteral walls.